Analytical tests for clinical or veterinary purposes, as well as for food testing, health and safety, and other non-diagnostic purposes in commerical, residential and recreational environments, vary considerably in the chemistries and complexities involved. Some of these tests involve a series of reagents or other materials and multiple steps, and many require controls to assure the user that the test has been properly performed and the result obtained is accurate and reliable.
In tests involving wet chemistry techniques, various aspects of the tests contribute to making the tests expensive, time-consuming and vulnerable to error. In tests where several reagents are needed, certain reagents cannot be mixed in advance due to a tendency to slowly react even before the addition of the critical species which the test relies on to drive the reaction. Some reagents begin to decompose as soon as they are placed in solution. Other reagents are unstable upon exposure to air or to air-borne moisture. For these and similar reasons, many reagents must be kept in separate containers prior to use, others require refrigeration or must be prepared fresh for each use, and those unstable in air must be kept in air-tight containers. The storage, maintenance and handling of the chemicals must therefore be done carefully to preserve the integrity of the test.
The procedures required for wet chemistry techniques using multiple reagents are likewise often cumbersome and time-consuming. Aside from the awkwardness of manipulating several chemicals using appropriate vessels and transfer devices and performing a series of steps in sequence, other factors add to the time required. For example, the concentration of an analyte in a test sample is often low, particularly when the sample requires dilution before use. This is the case for instance in samples which are extracted from a clinical swab or other sampling device. Low concentrations require long incubation times, often as much as several hours, to achieve sufficient reaction for a detectable result. Precipitated analytes can be concentrated by centrifugation, but this requires centrifugation equipment and decanting. Long incubation times are often needed for visual indicators since a visual indicator is typically dissolved in a common reaction mixture with other reagents, and thus diluted, the indicator requires a long incubation before a visible change occurs. This limits the sensitivity of the test as well.
For certain tests, the cumbersome procedures of wet chemistry techniques have been circumvented by the development and use of dry test panels, which are frequently made of paper or similar materials impregnated with reagents and visual indicators. In most cases, these panels still require additional implements, however, such as a pipet to apply the sample to the panel. Additional reagents such as developing solutions are also often required. Dilution and other types of pretreatment of the specimen are also required in many cases before the specimen can be applied to the panel. The equipment and materials involved are thus often more than the panel itself, and require maintenance, storage and replenishment. In addition, dry test panels are available for only a limited variety of tests.
Controls are included in many test procedures to assure that the test components are functioning properly and that the test has been properly performed, and to assist the technician performing the test in differentiating between positive and negative results. In wet chemistry techniques, this generally requires blank tests run in parallel with the sample test, doubling or tripling the number of materials and manipulations which the technician must perform. This can be avoided to some extent in techniques involving dry panel indicators, but the reliability of the controls is sometimes compromised. Controls which are not designed to be activated at the time of the test are susceptible to deterioration during storage. Those which are activated at the time of the test generally require separate applications. Finally, controls proposed for some dry panels feature only a positive control. This limitation compromises test results and may result in undetected false positive test results.
These and other problems and disadvantages of the prior art are addressed by the present invention.